Priority sequencing device



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Feb. 3, 1970 R. M. DUNN E'r AL 3,493,939

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United States Patent O 3,493,939 PRIORITY SEQUENCING DEVICE Robert M. Dunn and David R. Hadden, Jr., Eatontown, NJ., assignors to the United States of America as represented by tlle Secretary of the Army Filed Apr. 10, 1967, Ser. No. 629,824 Int. Cl. G11c 15/00; H03k 3/286 U.S. Cl. 340-173 S Claims ABSTRACT F THE DISCLOSURE A priority sequence storage device for writing priority information from an external memory into a memory array 1n the order of priority of the incoming words, the priority of which is represented by a combination of priority bits and characterized in that a word of given priority already stored in the memory array takes precedence over an incoming word of the same priority, wherein a control level is supplied to the memory array and is caused to travel through said array along a path, and to emanate from said array at a position, which path and position depends upon the relative priority of the external information and any information already stored in said memory array so that the incoming words are written in the proper order of priority into said memory array and so that priority words in said memory array can be read out in the order of priority.

BACKGROUND OF THE INVENTION In data processing applications it often is desirable to store items of information in the storage location in the order of priority. In many instances, the priority order has been established by the programmer. Such a software approach can result in complex programs which may have to be revised with changes in incoming information. In accordance with the invention, the information is written simply and inexpensively into the storage array in order of priority and the information can be read out quite simply in the proper order. This hardware approach is preferable to the programming approach and to certain systems of the prior art in which the information is written into storage in random fashion and then must be retrieved in order of precedence by somewhat elaborate and time-consuming controlled searching techniques.

SUMMARY OF THE INVENTION The device of the invention includes a memory array with m word positions or storage locations, each word position consisting of n bits arranged in order of signicance. The memory array has n cells for each word position in the memory array, or a total of mn cells. Each cell in a given word position includes a J-K type flip flop which stores the appropriate bit or character for the given word. For example, for a word 1010 stored in a given word position of the memory array, the assertion outputs of the J-K flip op of the four cells of that word position would be 1, 0, 1, 0 starting with the cell of the most significant bit. Consequently, the corresponding negation outputs of these flip flops would be 0, 1, 0, l, respectively. All cells of a given word position include common write, read (shift down) and shift up buses. All cells of a given bit position receive the assertion and negation outputs of the corresponding bit of a word located externally of the memory array which one desires to write into the memory array. Each of the cells comprises circuit logic for implementing an algorithm which will now be explained. Starting at the most significant bit, a comparison is made between the most significant bit of the external word and the most significant bit of all words in the memory array. If there is a disagreement in a given word, the memory cell of the most signicant bit of the given word position will produce a block level which is supplied to all succeeding cells in that word position. The second bit of the external word is compared in like fashion with the second bits of the words in the memory array, and so on, for other bits. A pattern of block levels thus will be established, each block level from the given cell being transferred to the cells :of the same word position and all bit positions of lower significance.

In writing an external word into the memory array, a control level is supplied to the cell of the most significant bit and least significant word position. The logic circuitry in this cell is such that, if a given bit of the external word is ZERO, the control level will be transferred across the cell to the cell of the next least significant bit in that word position. In other words, the cel] logic circuitry is such that, if a given bit of the external word is ZERO, the control level will move across exactly one bit in the memory array without moving downward. If there is a :one in a bit of the external word, the control level will be directed downwardly from the memory array cell corresponding to that bit and to that word position under consideration, and will be transferred to the cell of the same bit position and of the word position of next higher order of priority. The control level will continue to drop downwardly through all cells of that bit position until it either meets a cell in that bit position in the memory array which has a ONE in it or it meets a cell which contains a block level. When either of these conditions occur, the control level is transferred to the cell of the next least significant bit in that word position. In other words, if there is a ONE in the external word, the control level will drop until it either meets another ONE in the memory array or encounters a block, at which point the control level moves across one bit in the memory array.

The control level, after following a path through the memory array which will differ for different combinations of external word and words stored in the memory array, will emanate from a word position of the memory array which is of immediately higher priority than the word position into which the external word should be written. The control level thus emanating from the storage array then is used to energize the write bus of the cells in the word position immediately -preceding that from which the control level has emanated. The level on the write bus, together with the assertion or negation output from the cell of the external memory word bits, will enable a gate for actuating either the J or K input to the flip opvof that cell. The control level emanating from a cell in a given word position is applied to the shift up buses of cells of all word positions preceding the word position to be written into. The level on the shift up buses, together with either the assertion or negation output from the I-K flip iiops of these cells will enable a gate for actuating either the J or K input to the preceding ilip op, depending upon the bit of the word to be shifted. Upon arrival of a clock pulse, transfer of words in all word positions preceding the word position written into the immediately preceding word position is accomplished. The characteristics of the clocked J-K flip flop of the cells is such that the words can be shifting directly and non-destructively from one word position to the adjacent word position without need for such devices as dummy registers. When it is desired to read a word from the memory array, a read level is applied to the shift down buses of the cells of all word positions and the read level on the shift down bus, together with either the assertion or negation output from Patented Feb. 3, 1970 the cell of the immediately preceding word position will enable the gate actuating either the I or K input to the flip flop of the corresponding cell depending upon the bit of the Iword to be shifted. Upon arrival of a clock pulse, transfer of all words to the succeeding word position is accomplished.

summarizing, each word to be written into the memory array is inserted in the word position thereof which depends upon the priority of that word and those already within the memory array. The words are written into the memory array in their proper order of priority. When the memory array becomes full, an additional word to be written in must displace one of the words already in the full array. This new word will be written into the proper position in the order of priority and the word of lowest priority lwill be shifted off. When it is desired to read a word from the memory array, this may be done simply by applying the read level to the cells of the memory array, thereby shifting all words in the memory array one word position. The word nearest the output end of the memory array (the word of highest priority) will then be transferred into an output register. The next read level will transfer the Word of next higher priority, which will be the word shifted into the word position of highest priority to replace the word previously read out.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B is a schematic diagram illustrating an embodiment of a priority sequencing device according to the invention; and

FIG. 2 is a diagram showing the contents of a conventional cell used in the system of FIGS. lA and 1B.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the example illustrated, it will be assumed that each priority word has four bits and that the memory array has a capacity of six priority words. The number of bits needed will depend on the number of word positions in the memory array. It should be understood that each priority word forms a portion of a complete word which may have any number of bits, including operation codes, and information bits. In other words, each word stored in the computer memory contains many bits of which four (in this example) serve to indicate the priority of that word. In order to simplify an examination of this application, only the priority indicating portion of the complete word, hereinafter referred to as the priority Word, will be discussed. Whenever a priority word is transferred from one position to another in the memory array, it should be understood that the remaining portion of the word will shift along with the priority word.

For the sake of illustration, it will be assumed that the bits of the priority word from some external control unit are loaded into an external memory comprising registers IN1, IN2, INS, and IN4 such that the register IN1 will contain the most significant priority bit and the register IN4 will contain the least significant bit. The word position nearest the input will be referred to as the first word position. The words are written from the external memory into the memory array from top to bottom, in the illustration given, so that if the memory array is empty, the first word will be written into the last (in the example shown, the sixth) 'word position. As a result of the priority scheme of the invention, the word with the highest priority will be found in the sixth word position comprising cells E61, E62, E63 and E64. Similarly, the Word with the next highest priority will be found in the penultimate (fifth) word position cornprising cells E51, E52, E53 and E54, While the word with lowest priority (or, in the case of equal priority, the word last written into the memory array) will be located in the rst word position which comprises cells E31, E12, E13 and E14 The uppermost 4-bit word represents the external priority word to be Written into the memory array. The Iline and arrow thereon illustrates the path building of the external word through the memory array. In order to explain the technique for path building, comparison between the external word and the memory array must be established. The algorithm is as follows:

Starting at the most significant bit, a comparison is made between the first bit of the external word to be written into the memory array and the first bit of the first word in the memory array. If a word position in the memory array is empty, the registers of the bits of that word position will arbitrarily be set to zero, one (an assertion output of zero). If there is a disagreement between the first bit of the external priority word and the first bit of the first word in the memory array, said memory array bit receives a block. This block is indicated in Table I as a dash to the right of the bit. All following bits of that same memory array word will also receive blocks. The next comparison is made between the first bit of the external Word and the first bit of the second word in the memory array, and so forth across the memory array. Similarly, the second bit of the external priority word is compared with the various second bits of the memory array. When the entire memory array has been thus examined and the necessary blocks inserted, a bit may now be directed through the memory array to accommodate the external word.

If the external bit is a zero, the path will move across exactly one bit without moving down. If, on the other hand, there is a one in the external word, the path will drop until it either meets another one in the memory array or encounters a block. At this point, the path moves across one bit. The path across moves over the block or bit being compared.

Before describing the basic system of FIG. 1 in detail, reference will be made to FIG. 2 which is a schematic representation of a cell Emn of the memory array. First of all, however, it should be pointed out that there are some modifications made in certain of these cells. For example, all cells of the first word position, namely, cells E11, E21, E31, E41, E51 and E51 have n0 B Input to gates L and Z. Finally, all cells of the fourth bit position, namely, cells E14, E24, E34, E44, E54 and E64, need have no G, H and Z gates, since there is no need for B* outputs from these CCIIS. Cells E22, E23, E32, E33, E42, E43, E52 and E53 are exactly as shown in FIG. 2.

The lines An and 'n to the cell Emn carry available assertion and negation outputs of the external word register corresponding to the nth bit. For example, if the word in the external register 11 were 0111, the An and the Xn levels from external registers IN2, 1N3 and IN4 would be one and zero, respectively, while the An and 'n levels from external register IN1 would be zero and one respectively. The An and the 'n levels are supplied to all memory cells of the nth bit.

Also entering each cell Emn except for first Word cells as previously indicated, is a D line which is connected to the D* output line of the cell of the same bit position but of the immediately preceding word position; that is, :line D of cell Enm is connected to the D* output of cell E(m 1)n. Likewise, each cell Emu, except for the first bit cell, includes a B and a C input line which is connected to the respective B* and C* output lines of the cell of the same word position but of the immediate preceding bit position. In other words, lines B and C of cell Em both are connected to cell Em( 1).

Each cell Emn includes a register F which may lbe in the form of a J-K flip llop having I and K input lines and corresponding output lines Qm11 and 5mn. These output lines proceed from cell Emn and are connected to input lines Q(m+1)n and @ummm respectively, of cell E(m 1); in the case of the last Word cell, the output lines Qmn and 61m, are connected to the appropriate input lines of output registers OP1, OPZ, OP3 and OP4. The Q(m+1)n and 60mm, lines from cell E m+nn are connected to AND gates I and VI, respectively, of cell Emu. The other input to gates I and VI is connected to the SHIFT UP bus Lum of cell Emu. The Q(m 1) and (m 1)n lines from cell E(m 1)n are connected to AND gates II and V, respectively. The other input to gates II and V are connected to SHIFT DOWN but Ldm of cell Emu.

The input lines An and Kn are connected to respective AND gates III and IV of cell Emu. The other inputs to gates III and IV is connected to the WRITE bus LWm of cell Emu. It will be noted that there is a separate SHIFT UP, SHIFT DOWN and WRITE bus for each word position of the memory array and that a given one of these lines passes through all cells of a given word position.

The output line of AND gates I, II, and III of cell E,m1 are connected to an OR gate R and the output line of OR gate R is connected to the I side of flip op F for cell Emu. Similarly, the output lines of AND gates 1V, V and VI of cell Emn are connected to an OR gate S and the output line of OR gate S is connected to the K side of flip flop F of cell Emu.

A clock pulse CL is applied simultaneously to the ilip flop F of all of the cells of the memory array and any state transformations of a flip op occur only upon receipt of such a clock pulse. The clock pulse may be derived from a single clock source 12 and can be applied to all flip flops by closing switch 13 at some interval following either movement of switch 15 to the READ or WRITE position.

If any of the following three conditions is met, a level will be available at a corresponding input or OR gate L of a given memory array cell Emn. The rst condition is the nth bit of the external word is a zero; if this condition exists, there will be an input level n on input line a of OR gate L of cell Emn and also to other input lines a of nth bit cells. The second condition is that the nth bit of the nth priority word at cell Emn is a. one; if this condition exists, there will be an input level Qmn on input line q of OR gate L of cell Emu. The third condition is that the bit on line An of the external word, if any, and the same bit in the cell Enm of the memory array are different bits, there will be an input level B on input line b of OR gate L of cell Emu.

An OR gate P is receptive of either (but never both) a C level from the cell Em( 1) and of a D level from cell E(m 1)n.'l`he output on line P1 of OR gate P is applied to an AND Gate X which also receives the output of OR Gate L by way of line L1. The output, if any, from OR gate X is referred to as C*. The condition for a C* level from any cell in the memory array then may be expressed by the following logical equation:

were Bm(n 1) is the blocking level, if any, gate Z of the cell Emmgl) presented to cell Emn, Qmn is the affirmation output from ip flop F of cell Emn and mn is the negation output of the external word bit An presented to cell Emu and Cmn and Dmn (only one of which is obtained for a given cell) are the levels obtained from the immediate preceding cell Em(n 1) and E(m 1)n, respectively.

If one or more of three conditions is met, no level will appear at any of the inputs to OR gate L of cell Emu. Firstly, if there is a ONE in the nth bit An of the external priority word, there will be no input on input line a of OR gat-e L of cell Emu. Secondly, if there is a ZERO in the nth bit of a word in the nth position of memory array 10, there will be no input on input line q of OR gate L of cell Emn. Thirdly, if there is disagreement between the (n-l)th bit in the external word and the corresponding (n-l)th bit of the word in the memory array, that is, if one bit is a one and the other bit is a zero, there will be no input on line b of OR gate L of cell Emu. T he preceding remarks can be restated as follows: If all three of the following conditions occur simultaneously, there will be no output from gate L. First, the nth =bit from the external memory is a one; second, Qmn is a zero; and third, An and Qmn are different binary characters.

If the blocking level presented to a given cell Emn of the memory array 1t) is represented by B from the cell Em( 1), mn is the negation output of the ilip flop from cell Emn and An is the affirmation output from the flip flop of the nth bit of the external word presented to cell Emu, the condition for a D* level from cell Emn then may be expressed by the following logical equation:

D*:(QmnAnFm(n-1)) where C and D are the input levels to cell Emn obtained from one or the other (but not both) of the respective output gates X and Y of the cell E(m 1) or cell Em(n 1), as the case may ibe.

Whenever the Q output of flip flop F of cell Emn is a ONE and the nth external word bit is a ZERO, AND gate G will be enabled, as also will be OR gate Z, and a B* output will be obtained at cell Emu. On the other hand, the output of the flip flop F to cell Emn is a ZERO and the nth digit of the external word is a ONE, AND gate H is enabled, as is also gate Z; again a B* output is obtained at cell Emu, this input also will enable OR gate Z and a B* output will be obtained at cell Emu. This is in line with the statement made previously that a block pulse, once obtained, is produced for all other bits of the word in the memory array.

If either a C or D pulse level appears at cell Em11 and an output is available at OR gate L, under conditions already described, AND gate X is enabled and a C* output is available at cell Emn. If, however, there is no output at OR gate L coincidentally with the presence of either a C or D level at cell Emn inhibit gate Y is enabled and a D* output is obtained at cell Emu. It Will be noted that only one of the gates X and Y of any particular cell Em, can be enabled at any time. In other words, if a C* level emanates from gate of cell Em, there can be no D* level emanating via gate Y of the same cell. The decision as to which path through a cell in word position m and bit position n in the control level from generator 17 will pass will be determined on the basis of comparison of the nth bit in the external priority wor-d and the corresponding nth bit of the Word m in the memory array.

When it is desired to SHIFT information down the memory array, switch 15 is moved to the READ position and a one level from generator 17 is supplied to all SHIFT DOWN lines of the ymemory array. In order to explain the SHIFT DOWN or READ operation, it will be assumed that the last (sixth) word position in the memory array contains the word 0101 and that it is desired to READ this word out of the memory array into the output registers OP1 to OP4. It will further be assumed that the preceding word position (fifth position) of the memory array is empty. Consequently, the aforementioned outputs is no B input to any of the first bit cells of the memory array; hence, there is no input on line b of OR `gate L of cell E11. In other words, gate L of cell E11 is closed and no output appears on OR gate line L1. It follows that the AND gate X is not enabled and that no output of the flip flops of the fifth word position of the memory 5 level C=z appears at cell E11. Since there is an input on array will be 000.0. If, now, the READ (SHIFT DOWN) line P1 of AND gate Y, together with no input on line Lem is energized by moving switch 15 to the READ inhibit line L1 of AND gate Y, conditions are proper position, the operation will be as indicated in the followfor an output level to appear on output line Y1 of `gate Y ing Table III. As an aid in explaining Table III, Table II l0 of cell E11. Consequently, a level appears at the De output will first be presented showing the operation of the J-K line from cell E11. flip flop in the various cells of the memory array. The incoming control level from generator 17 thus TABLE 11 moves downwardly from cell E11 and is transferred to 1 the first bit cel-l E21 of the second word position. In other 111111 lll.. 15 words, the D* output from cell E11 now becomes a State Q J K Resulting D input to cell E21 and passes OR gate P of cell E21. 1 1 0 1 Since Q11, Q12, Q13 and Q14 are all ZERO, there can be (l) (l) (l) no output from AND gate G of respective cells E11, E12, 0 0 1 0 E12 and E14. Likewise, since A1, A2, A3 and A4 are all 20 ZERO, there can be no output from AND gate H of TABLE Hr Register Register Cell Initial Bus AND Gate OR Gate FF Input Resulting Emu Qmu Q01-1) Energized Enabled Enabled Activated mn Eel.--" 0 I Lum V S K 0 E.-,2 i 1 d... V S K o E63..." 0 1 Ld, V S K 0 E64-.." 1 1 Lum V S K l) Upon arrival of a clock pulse CL to the ip ops of 30 respective cells E11, E12, E13 and E11. With no input the cells of the memory array, the afrmation outputs from line b of OR gate Z of cell E11, there can be of all cells of the last (sixth) word position will be 0000, no B* output from cell E11. Consequently, there is no indicating that the priority word previously in the memory B input to cell E12 or to cells E13 and E14 and there array (viz., 0101) has been read out of the memory array. can be no input to line b of OR gate L of cells E12, E12 The bits formerly in word position 6 then are transferred 35 and E14. In other words, OR gate L of cells E12, E13 and to corresponding output registers 01 to 04. The word E14 is closed and `OR gate Y of these cells necessarily 0000 remains at the sixth word position of the memory is closed, The input control level from generator 17, array until the next execution command level (SHIFT therefore, cannot cross cell E11 to any of the other cells DOWN, SHIFT UP 0I WRITE) OCCUTS at 011e of the E12, E13 and E11 of the first word position, since gate X buses Ldm, L111n or Lwm. 40 of these cells is closed. Since the ip flops of all cells Having emptied the memory array, it will be assumed have been reset to the ZERO condition as a result of further that the priority word 1101 is to be written into previously reading out all words from the memory array, the memory array. The switch 15 is placed in the WRITE the Q output of cell E21 is ZERO and no input appears position and the control level from generator 17 appears on line q of gate L of cell E21. Since the iirst bitof the at the C UPJt lille 0f the flfet een E11- AS PfeVleUSlY 40 external word is a ONE, the level at line 1 is a ZERO noted, none ofthe other irst bit cells have such a C input and there 1s 11e 11111111 011 line a of gate L of een Em line. This C level from generator 17 forms an input to There 1S 1-10 B 11113111 to een E21 Therefore, 0R gate L 0R. gate P 0f een E11, and, although Cell E ii has 110 of cell E21 is closed and, as in the case of cell E11, the D input, en Output level appears at Output Ime AP1 ef AND gate X of ceu E21 is ciosed and gare Y of Celi E21 OR gate P- A ZERO and a ONE 1S aPPhed t0 gates 50 is enabled. An output D* thus emanates from cell E21 H and V, l'eSPeelVely, 0f all first Werd eeue- Gates and is transferred by way of input line D of cell E31 II and V have received an input level from SHIFT to the OR gate P of een ESP DOWN Ime Ldm durmg the PUOI READ operallon and It is now evident that there will be no output on line L1 the gates V and S are enabled. The K side of flip Iflop F of OR ate L of Cells E E E d E u 55 e ai, 4i, 51 an 61, Since a of cell E11 Will be activated upon receipt of clock pulse CL Qm11 outputs of these cells are ZERO, the A1 input to all and Q11 and Q11 of cell E11 will be a ZERO and a ONE,

of these cells is ZERO and there is no B input to any of respectively. Likewise, gates V and S of the rst word these cells. Consequently, the AND gate X of all these cells E12, E13, and E14 will be enabled, the K side of the u 1 1 flip flops of these cells will be activated and Qmn of these Ce S W1 1 be c Osed and the AND gate Y of au these cells cells Win be a ZERQ Since Q11 is ZERO there is no 60 will be enabled. As a result, the control level from geninput on line q of OR gate L of een E l 1. Likewise, there erator 17 proceeds down through all of the lirst bit cells is no input O11 hne q of gate L of Cells E12, E13 and Ele of the memory array and emanates from the D* line Moreover, since the first bit from the external memory 0f C611 'Eei- This D* OUPUt Passes OR gate T and enelflip ilop is a ONE, A11 is ZERO and there is no input 65 glzee the WRITE bus Lw1 0f the fst Word POSOH- The on line a of OR gate L of cell E11. The same is true writing operation may be described by reference to for cells E12, lE13 and E14. It should be noted that there Table IV.

TABLE IV Priority AND Word Initial Bus Gate En- OR Gate F Input Resulting Cell Eum Bit An mn Energized abled Enabled Activated mn Einw--- 1 0 La iii R J i i 0 Lw iii R J i 1 o Lw iii R I i Eeuw.-- 0 o Lw@ iV s K 0 11 Initially, the word 0110 is stored in word position four of the memory array. In other words, the active lines from the C6115 0f E41, E42, E43 and E44 are Q41, Q42, Q43 and Q44, respectively. These outputs become inputs to the respective cells of lf he immediately preceding (third) Word position; that is, the lQ outputs of cells E41, E42, E43 and E44,

In other words, the Qn outputs of cells E61, E62, E63 and E54 of the sixth word in the memory array are 1, l, 1 and 0, respectively, indicating that the Word 1110 originally in the external memory IN1-IN4 has been Written into the last Word position of the memory array.

In accordance with the invention, if a priority word of lower priority were to be made available at the external memory IN1 to IN4, this word, upon receipt of the next WRITE signal from generator 17 and triggering by the succeeding clock pulse CL, would be transferred into the fifth word position of the memory array, that is, the memory position immediately above the priority word already in the sixth or last word position of the memory array. This process would be repeated so long as successive priority words were presented to the external memory, in their order of priority, until all Word positions of the memory array are filled.

It will now be assumed that the rst through sixth Word positions of the memory array have been lled with priority words in the following order 0001, 0010, 0101, 0110, 1010, and 1110, and that the priority Word loaded into the external memory which is to be written into the memory array is 0111. The manner in which the control level from generator 17 passes through the memory array can be shown by resort to Table V.

10 directly to the WRITE bus LW4 of the `word position (fourth position) immediately preceding the Word position (fifth position) from which the control signal emanates.

At this time, all other WRITE buses Lw1 to Lwa, LW5 and LWS Will be inactive since none of the cells E41, E42, E43, E44 and E64 will have C# outputs. With the WRITE bus Lw4 active, and with ZERO input at line A1, gate IV of cell E41 Will be enabled, and an input control level Will be applied by way of gate S to the K input of flip flop F of cell E41. Since the Q output of the flip flop F of cell E51 was a ZERO, the K input tot he flip flop of cell E41 will not change the state of the flip flop and the Q output will remain a ZERO. Similarly, With a ONE input at lines A2 and A3 feeding cells E42 and E43 gate III of these cells will 4be enabled and an input control level will be applied by Way of OR gate R of cells E42 and E43 to the I input of the flip flop of cells E42 and E43. Since the Q output of the Hip flops of cells E42 and E42 were ONES, the Q input from cells E42 and E43 will remain ONES. Finally, with a ONE input at line A4 to cell E44, gate III of cell E44 is enabled and an input level is applied by Way of Gate R to the I input of the flip flop of cell E44. Since the Q output from the ip flop of cell E44 was a ZERO, this flip flop will change state and its Q output will be- TABLE V Gm Hum Bum B*mn Cm Dm Pm Lmn C*m DH1 B (m-i) n Qms-l- Lmn- Emu- Gmom..+ L+ omn+ (cm1- Qmn Qmn An An Quin-Au QmrrAn B* mi)n Hmm C*(m1)n D*m(n1) Dum Bmn Emu Dmn) Dmn) l 0 1 0 (l 0 1 1 1 0 1 0 1 1 0 (l 1 0 1 1 1 0 l. 1 1 1 0 0 1 1 1 0 0 1 0 0 0 0 1 0 X X 1 X 0 1 0 0 0 1 0 1 0 0 0 0 1 (l 0 1 1 0 0 l (l 1 0 1 1 0 1 0 1 1 0 0 l. 1 0 0 1 0 0 1 1 0 X X 1 .X 0 l 0 0 0 1 0 1 0 0 0 0 0 1 O 0 0 0 1 0 (l 0 0 0 0 1 1 1 (l l. 0 1 1 0 O 1 0 l. 1 0 1 1 (l 1 0 1 0 X X 1 X 0 l. 0 0 (l Gum Hm Bm B*mn Cm Dmu Pm Lm Chun Din B (m-l) n' Qmn-:l' Linn' Emu H Gm- 044+ .14+ cm+ om+ Qmn Qms An h Qmn-'An Qmn-An B*(m1)n Hmn C*(m1)n D*m(=u Dm Bm mn Dm) Dm) 0 1 (l 1 0 0 0 0 0 1 0 0 1 0 1 0 0 0 0 0 0 l 0 0 O 1 0 l 0 0 0 0 0 0 1 1 1 0 1 0 1 1 (l X X 0 X 1 1 0 l. (l 1 l. 0 0 l 1 0 1 0 0 1 (l 0 0 0 1 1 1 1 1 0 0 1 0 O 0 1 0 1 0 0 0 1 1 0 0 l 0 0 0 0 1 1 0 X X 1 X 0 l. 1 1 (l 1 (l 1 0 0 1 1 0 1 0 1 0 0 0 1 0 1 0 0 0 1 1 0 0 0 l. (l 0 0 1 0 1 0 0 0 l. l. 0 0 0 1 O O 0 (l 1 l 0 X X 1 X 0 0 1 0 0 0 The dashes in the table indicate that no physical inputs can exist and the crosses indicate that no physical outputs are possible. For example, there are no D inputs to cells of the first Word position, namely, cells E11, E12, E13 and E14. For this reason, AND gate P is superfluous. In the case 0f cell E11, the level from signal generator 17 can be applied directly over C line of cell E11 to gates X and Y of that cell. In the case of all cells of the first (most significant) bit, except for cell E11, there are no C inputs; therefore, any D input can be applied directly to the gates X and Y of that cell. In the case of all cells of the fourth (least significant) bit, there is no need for a block level Bi; consequently, gates G, H, and Z may be omitted and the absence of any output therefrom is indicated in the Table V by the crosses. It can be seen from Table V that the control signal level appears successively at the C* output of cell E11, the D* output of cell E12, the D* output of cell E22, the C* output of cell E32, the D* output of cell E33, the C* output of cell E43, the D* output of cell E44 and the output of cell E54. The path through the memory array is indicated by the heavy dashed line. The control signal at output line C* of cell E54 is applied come a ONE. The present Q outputs of cells E41, E42, E43 and E44, then, are 0, 1, 1 and 1, respectively. In other words, the word 0111 from the external memory has been written into the fourth word position of the memory array. This obviously is the correct position for the word 0111 since 0111 is of greater Weight than the rst four words in the memory array (viz., Words 0001, 0010, 0101 and 0110) but of lesser Weight than the Words 1010 and 1110 in Word positions ve and six of the memory array.

Since the Word 0111 from the external memory has been Written into the fourth word position, it obviously is necessary to shift up the words in the rst four word positions of the memory array. This is accomplished by energizing the SHIFT UP buses 1.114, L23, L22 and L21. The control level emanating from the C* line C*54 of cell E54 passes OR gage U2 enroute to SHIFT UP bus L15 of the third Word position of the memory array. This output of cell E54 also passes through OR gates U2 and U3 enroute to SHIFT UP bus L22 of the second word position of the memory array and via OR gates U2, U3 and U4 to the SHIFT UP bus 1,111 of the first word position.

13 The Tables VIII and IX indicate, by way of example, that, for an external word 0101 and a priority word 0101 already in the third word position of the memory array,

the control level from generator 17 will proceed acrosscell En to cell E12, down cell E12 to cell E22, down cell E22 to cell E32, across cell E32 to cell E33, across cell E33 to cell E34 and across cell E34 to the C* output line thereof. The control level from generator 17 then appears on the WRITE bus LW2 of the second word position of the memory array. Upon arrival of the next clock pulse CL to the flip ops of cells E21, E22, E23 and E24, these flip flops will be actuated and the word 0101 from the external memory will -be Written into the second word position. Likewise, the control level from the C* line of cell E34 will pass through gate U4 to the SHIFT UP line Lul of the first word position to shift the Word 0010 formerly in the second word position to the first word position and, in effect, shifting the word 0001 off the memory array.

This completes the description of the preferred embodiment of the invention illustrated herein. However, many modifications thereof will be apparent to those skilled in the art. Accordingly, it is desired that the invention not be limited by the particular details of the embodiment described herein except as defined by the accompanying claims.

What is claimed is:

1. A priority sequencing device comprising a priority memory array having a storage capacity of m priority words, said memory array including mn cells where m is the number of priority word positions in said array and n is the number of priority bits per memory word, external storage means into which is loaded an external priority Word to be presented to said memory array, means for applying a control level to the cell of the lowest priority memory word position and of the most significant bit, said cells each including logic circuitry for controlling the path through the cells of said memory array taken by said control level and also the memory word position from which said control level emanates from said memory array in accordance with the relative priority of the aforesaid memory words.

2. A priority sequencing device according to claim 1 'wherein the memory cells except those for the least siginiicant bit each have a first output line connected to the cells of the same memory word position and of the =bit of next lower significance, and the memory cells except those for the memory word position of lowest priority having a second output line connected to the cell of the same bit and of the memory word position of next higher priority.

3. A priority sequencing ldevice according to claim 2 further including a set of execution command lines for the cells of each of said memory word positions, the control level emanating from said array energizing one of said command lines of the immediately preceding memory word positions for writing said external Words into the latter position, and the control level emanating from said array energizing another of said command lines of `all memory word positions preceding the memory word position written into for shifting the contents of all said preceding memory word positions to an adjacent memory word position nearer the external storage means.

4. A priority sequencing device according to claim 3 further including means for deriving a block level at la cell of a given bit in the memory array and at cells of bits of lower significance in the sarne memory Word position wherein said given tbit disagrees with the corresponding bit of the word in the external memory, said block level preventing transfer of said control level to said second output line.

5. A priority sequencing device accor-ding to claim 4 further including means for transferring said control level incident on a cell of a given bit to the rst output line thereof when the corresponding bit of the external word is a zero, and means for transferring said control level incident on a cell of a given bit to the second output line thereof when the corresponding bit of the external word is a ONE and when there is no block level at said cell.

6. A priority sequencing device according to claim 1 further including a set of execution comm-and lines for the cells of each of said memory word positions, the control level emanating from said array energizing one of said command lines of the immediately preceding memory word positions for writing said external words into the latter position, and the control level emanating from said array energizing :another of said command lines of all memory word positions preceding the memory Word position written into for shifting the contents of all said preceding memory word positions to an adjacent memory word position nearer the external storage means.

7. A priority sequencing device according to claim 6 further including means for deriving a block level at a cell of a given bit in the memory array and at cells of bits of lower significance in the same memory Word position wherein said given bit disagrees with the corresponding bit of the word in the external memory, said block level preventing transfer of said control level to said second output line.

8. A priority sequencing device according to claim 7 further including means for transferring said control level incident on a cell of -a given bit to the first output line thereof when the coresponding bit of the external word is a zero, and means for transferring said control level incident on a cell of a given bit to the second output line thereof when the corresponding bit of the external word is a ONE and when there is no block level at said cell.

References Cited UNITED STATES PATENTS 2/1966 Roth 340-1725 l/l967 Koerner et al. 340-1725 X UNITED STATES PATENr QFFICE CERTIFICATE OF CORRECTION Patent No. 3,493,9394 February 3, 1970 Robert M. Dunn et al.

It. is certified that error appears in the above identified patent and that said Letters Patent are hereby 'corrected as shown below:

Column 6, line `19, "at" should read -v :from same line49, after "Emu" cancel the comma and insert If a B input is obtained at cell Emn,`; line 63, after "gate" insert X Column 7, in the heading to TABLE II, "Resulting" should read 4 Resulting Q same column 7, inthe head-ingto TABLE III, "Q(ml)n" should read m l)n Columns 9 and l0, TABLE V, bottom portion, column l, Iine 3 thereof, "E32" should yread E43 Columns ll and 12, TABLE IX, bottom portionf: In the column headed Qmn, change thedigit for E52 from "l" to 0 and the digit for E53 from "D" t'o -l in the column headed Q'mn, change the digit for E52 :from "O" to l and the digit for E53 from "l" to O l In the column headed An, for E52, change "0" to l for E53, change "l" to 0 In the column `headed A n for E52, change "1" to 0V for E53, change` "o" to 1 fol" E62, change- "l" to -4- for E63, lChange "O'Vto l In the column headed Gum, for E52, Change "1" to 0 fgr E53, change "0" to' l for E62, change "Il" to D for E63, change ,"0" to l In the columnheaded Hmn, for E52, change t0 1 S for E53', change "l" to 0 In the Column headed Bmn, 015,552 ,Change 1" to O g for E53, Change ont to, 1 In Vthe CQlUmIl haded Lmn, fQI Eszrrchange Ulu to 0 for E53, changeh "O" to --Vl In thercolumn headedmn, for E52,

change "0" to --4 l'; Afor E53, Change "l" to 0 Signed and sealed this 22nd day of December 1970.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. l v WILLIAM E.A SCHUYLER, JR. Attesting Officer l A i Commissioner 'of Patents Y 

